Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. The air pollutants may include both gaseous and solid material, such as, for example, particulate matter. Particulate matter may include ash and unburned carbon particles and may sometimes be referred to as soot.
Due to, among other things, increased environmental concerns, exhaust emission standards have become more stringent. The amount of particulate matter and gaseous pollutants emitted from an engine may be regulated depending on the type, size, and/or class of engine. In order to meet these emissions standards, engine manufacturers have pursued improvements in several different types of engine technology, such as fuel injection, engine management, and air induction, to name a few. In addition, engine manufacturers have developed devices for treatment of engine exhaust after it leaves the engine. This area of technology may be referred to as after-treatment.
Engine manufacturers have employed exhaust treatment devices called particulate traps to remove the particulate matter from the exhaust flow of engines. Particulate traps may include a filter formed of a filter material designed to trap particulate matter. The use of a particulate trap for extended periods of time, however, may enable particulate matter (which includes soot and ash) to accumulate on the filter, thereby causing the filter to reduce in effective volume and resulting in a decline in engine performance.
One method of restoring the performance of a particulate trap may include regeneration. Regeneration of a particulate trap filter system may be accomplished by thermal regeneration, which may include increasing the temperature of the filter and the trapped particulate matter above the oxidation temperature of the particulate matter, thereby burning away soot collected in the trap.
This increase in temperature may be effectuated by various means. For example, some systems employ a heating element (e.g., an electric heating element) to directly heat one or more portions of the particulate trap (e.g., the filter material or the external housing). Other systems have been configured to heat the exhaust gases upstream from the particulate trap, allowing the flow of the heated gases through the particulate trap to transfer heat to the particulate trap. For example, some systems may alter one or more engine operating parameters, such as air/fuel mixture, to produce exhaust gases with an elevated temperature. Running an engine with a “rich” air/fuel mixture can elevate exhaust gas temperature. Other systems heat the exhaust gases upstream from the particulate trap, with the use of a burner that creates a flame within the exhaust conduit leading to the particulate trap.
Nevertheless, even with regular regeneration, particulate traps may periodically require service, wherein a cleaning process is used to remove accumulated ash. Because the process of servicing a particulate trap is not trivial and can take some time, the trap is often removed from the engine/vehicle for service and can be replaced with another trap to minimize downtime for the engine/vehicle.
The replacement traps are not necessarily new and are often previously used traps that have been serviced (i.e., cleaned). Particulate traps may lose some efficiency/performance over the course of their service life, such that, even after being serviced, the trap may not perform up to the same standard as when new.
Because of this degradation in performance, regulatory agencies may require proof, or at least evidence, that any replacement particulate trap installed on an engine/vehicle has not been in service for any longer than the engine to which it is being connected. That is to say that the regulatory agencies expect a certain amount of degradation in emissions performance of an engine and after-treatment system over time. Engines are “certified” by the regulatory agencies with the understanding that the performance will not degrade more than a predetermined amount. However, if a particulate trap that is older (in terms of service life) than engine on which it is installed, the overall emissions performance may become substantially less efficient at that stage of the engine system's life than was expected of a certified system.
Systems have been developed that monitor the service life of particulate traps. For example, U.S. Patent Application Publication No. 2006/0005534, issued to Wirth et al., discloses a particulate-filter service-life determination unit. The system of the '534 publication, however, does not disclose a device that is specific to each particulate trap, independent of the engine. Instead, the '534 publication discloses that the particulate-filter service-life determination unit is based on a system that measures exhaust parameters associated with the particulate trap, such as pressure drop across the filter. That is, the system measures pressure drop across any filter installed in the exhaust system. Consequently, there is nothing tied to the particulate trap to indicate how long the trap has been in service. Thus, if the trap is removed from the device, serviced, and then replaced, there is nothing to indicate how long it has been in service.
The present disclosure is directed at improvements in existing engine exhaust after-treatment systems.